<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <script type="text/javascript" src="lib/vue.js"></script>
</head>

<body>
    <div id="app">
        <ul>
            <li v-for="aa in arr">{{aa}}</li>
        </ul>
    </div>

    <button onclick="add()">add</button>

    <script>
        function add() {
            console.log('run');
            //app.arr[1]='ddd';
            Vue.set(app.arr,3,'ddd')
        }
        var outData={
            arr:['aaa','bbb','ccc']
        };
        var app=new Vue({
            el:'#app',
            data:outData
        })
    </script>
</body>

</html>